The present invention relates generally to apparatus for plasma etching semiconductor wafers and more particularly to a high pressure, high etch rate reactor for etching a single semiconductor wafer.
In the fabrication of semiconductor devices, the use of plasma etching has several advantages over conventional wet etching. Among these are anisotropy, better resolution, and the elimination of problems inherent in the use of wet etch chemicals. Further, the use of single wafer, plasma etching systems offers the advantages of higher etch rates and improved etch uniformity as compared to multiple wafer or batch-type reactors. As linewidths decrease, for example, in very large scale integrated circuit devices, etch uniformity, or achieving a uniform etch rate across the surface of the wafer, and wafer-to-wafer becomes even more critical because of the increased number of devices on each wafer.
Single wafer, parallel plate plasma reactors are disclosed in U.S. Pat. No. 4,209,357 to Gorin et al., entitled "Plasma Reactor Apparatus", and U.S. Pat. No. 4,324,611 to Vogel et al., entitled "Process and Gas Mixture for Etching Silicon Dioxide and Silicon Nitride". The latter patent describes the use of secondary and tertiary reactive gases in a conventional reactor, and the former patent describes a reactor wherein the upper electrode includes both reactive gas supply means and exhaust means. In U.S. Pat. No. 4,297,162 to Mundt et al., entitled "Plasma Etching Using Improved Electrode", the reactor includes a curved upper electrode which is said to improve etch uniformity across the surface of the wafer. In some of these systems a wafer is fully exposed to the upper electrode, in other systems, such as the one disclosed in U.S. Pat. No. 4,367,114, an insulating ring is used as a partial confining wall and clamps the wafer to the lower electrode to ensure electrical contact. In such systems, the edge portion of the wafer that is clamped cannot be used for the fabrication of integrated circuit devices.
Current low (&lt;100 microns) and medium pressure (&lt;500 microns) plasma systems have exhibited relatively low etch rates and correspondingly long etch times, particularly when etching films greater than about one micron in thickness. In addition, when reactive gas pressure and RF power are increased in an attemmpt to increase the etch rate, the etch uniformity is degraded with an accompanying decrease in yield.